2000 gt Alignment Qs
09-15-2010, 03:16 PM
#1
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2000 gt Alignment Qs
RR tire failed inspection and is much more wore down than the others so I figure alignment is off. Also have four new wheels coming in so I should get an alignment correct?
Why would I have this problem with my tire if its a solid rear axle? Shouldnt I only need a front 2 wheel ( front ) alignment? ....stock springs btw.
Why would I have this problem with my tire if its a solid rear axle? Shouldnt I only need a front 2 wheel ( front ) alignment? ....stock springs btw.
09-15-2010, 09:11 PM
#5
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How many miles on the tires/car, what was the wear pattern of the RR tire, were the tires ever rotated during their service life?
Have you ever changed the axle lube, do you know if it was ever changed?
Have you ever changed the axle lube, do you know if it was ever changed?
09-15-2010, 09:44 PM
#6
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Just hit 75 K on the car. Those tires had about 25K on them . They were all uniformly wearing down except the right rear middle track was really worn down. Never rotated and I really didnt drive it that hard.
Pretty sure the axle lube has never been changed as I didnt know it was something you had to change. Where does the grease go?
Pretty sure the axle lube has never been changed as I didnt know it was something you had to change. Where does the grease go?
09-15-2010, 09:59 PM
#7
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Engine torque on acceleration causes the right rear tire to be unloaded--it doesn't matter whether you drive "hard" or not, it happens to some extent every time you accelerate and over 25k miles (without rotating the tires) it will cause the right rear tire to slip and wear.
Paradoxically the traction lock rear-end will not aid this unless you do drive hard. The traction lock depends on side thrust from the spider gears to load the clutches, so the "softer" you accelerate the lesser the load applied to the t/l clutches, and the lesser the lock-up.
This is an excerpt from this great suspension article [formatting applied]:
Short story it's normal wear, partially a result of not rotating the tires--if it were alignment related the wear pattern would be uneven--inside/outside/cupping/etc.
Paradoxically the traction lock rear-end will not aid this unless you do drive hard. The traction lock depends on side thrust from the spider gears to load the clutches, so the "softer" you accelerate the lesser the load applied to the t/l clutches, and the lesser the lock-up.
This is an excerpt from this great suspension article [formatting applied]:
The first thing the pinion gear tries to do is climb the ring gear. This forces the nose of the rear axle upward. As the car begins to accelerate, the torque leverages the front of the car upward, causing weight transfer to the rear. As viewed from the rear of the car, engine torque twists the body clockwise, lifting the left front and compressing the right rear (passenger-side) spring.
As the pinion continues to apply this massive torque through the ring gear, the rear axlehousing is also being leveraged in a counterclockwise direction as viewed from the rear--lifting the right (passenger) side of the axlehousing while planting the left. As the car accelerates, it appears to be planting the right rear tire when in fact axle torque motion is unloading the tire, reducing traction.
That is why a car equipped with an open differential will spin the right rear tire even under light acceleration. Limited slips are used to improve traction, but as you can see, they are merely a Band-Aid on the real problem. By using proven chassis modifications and tuning techniques, it is possible to equalize the load onto both rear tires.
As the pinion continues to apply this massive torque through the ring gear, the rear axlehousing is also being leveraged in a counterclockwise direction as viewed from the rear--lifting the right (passenger) side of the axlehousing while planting the left. As the car accelerates, it appears to be planting the right rear tire when in fact axle torque motion is unloading the tire, reducing traction.
That is why a car equipped with an open differential will spin the right rear tire even under light acceleration. Limited slips are used to improve traction, but as you can see, they are merely a Band-Aid on the real problem. By using proven chassis modifications and tuning techniques, it is possible to equalize the load onto both rear tires.
Last edited by cliffyk; 09-15-2010 at 10:03 PM.
09-16-2010, 12:33 AM
#8
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Just hit 75 K on the car. Those tires had about 25K on them . They were all uniformly wearing down except the right rear middle track was really worn down. Never rotated and I really didnt drive it that hard.
Pretty sure the axle lube has never been changed as I didnt know it was something you had to change. Where does the grease go?
Pretty sure the axle lube has never been changed as I didnt know it was something you had to change. Where does the grease go?
09-16-2010, 12:45 AM
#9
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09-16-2010, 06:41 AM
#10
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When the load is lessened during acceleration, as described above, the tire becomes "overinflated" for the duration of the lesser load--what the OP describes is the classic RWD open-differential tire wear pattern.
Once the LSD clutches are slipping (as in any turn) and at light loads the traction lock differential behaves quite like an open-differential--thats why the serious racers replace them with true locking units...
Once the LSD clutches are slipping (as in any turn) and at light loads the traction lock differential behaves quite like an open-differential--thats why the serious racers replace them with true locking units...